Telephone system.



W. F. GRADO-LPH W. O. HAHNE.

TELEPHONE SYSTEM.

APPLICATION FILED FEB. 1, 1908.

latented May 'ZQ IQQO.

4 sEEE s-sHEET '1.

W. P. GRADOLPH & Wye; HAHNE.

TELEPHONE SYSTEM.

APPLICATION FILED FEB. 1, 1908.

Patented May 24, 1910.

4 SHEETS-SHEET 2 lJ EF.

j, A? m Wm. 61 be,

W. F. GRADOLPHKEWEG. HAHNE TELEPHONE SYSTEM.

APPLICATION FILED FEB. 1, 1908.

Patented May 24, 1910.

4 SHEETSSHEBT 3.

W. F. GRADOLPH & W. G. HAHNE.

TELEPHONE SYSTEM.

APPLICATION FILED FEB.1, 1908.

9 3 I Patented May 24, 1910.

4 SHEETS-SHEET wrLLIA'ni I;

once, ILLINOIS,

emoLrH, or .s'r. Lours,'mrssouar, AND WILLIAM o; IH KNE, or 0111*essrcuons 'ro GRADOLPH. ELECTRIC comrimy, or s'r. LouIs,

MISSOURI, A COBPORA'IlION OF MISSOURI.

l 4 Specification of Letters I atent.

TELEPHONE srs'rnm.

Originalapplication filed December 9-0, 1965, Serial No. 292,529.Divided and. this application filed February 1, 1908. Serial N0.413,854.

To all whom it may concern:

Be-it known that we, \VILLIAM F.

none}; zens of u'set'ul Improvements in Telephone Systems,

variety of generating or for instance, thejtransmis'sionof speech, for.powe'r,

' that the sound waves of the .of which the taining'a full, clear datingcurrents,

.prises various and to a greater degree,

following is a'specification conande'xact description, reference beingha to the accompanying drawings frorming' a part hereof. r

Oiir invention-relates to the transmission of electrical energy by meansof electrical waves of alternating, intermittent, or undu andparticularly such waves as are employed in the electrlcal transmis sionof speech c1aimed. 4 I 7 Our. invention is applicable to a greattranslating devices;

and' for electric signaling. The-present application is a divisionalapplication from the application filed by us December 20, 1905, SerialNo. 292,529.

. It is well understood that the successful transmission of speechdepends not only on of the sound proreceiver, but also,

the volume or loudness duced by the telephone current is essentinctness.The telephone tially alternating, but its waves or impulses were over anelectrical conductor of great 1 are exceedingly complex, due to the facthuman voice, not

which 1 'roduce the current waves, are

' simple waves but are composite, being the resultants of numerouswaves, corresponding to overtones and harmonics, as well as of differentamplitudes and may be quite accurately trical waves by the transmitter;and if the current waves be transmitted over the'line with theircharacteristics substantially unimpaired or. unmodified, the sound wavesinto'which they are translated by the receiv-' ing apparatus willbesubstantially, identical,

at least as regards distinctness or clearness, with the sound Waveswhich affected the transmitter. Conse uently anything which disturbs theinter-re ation of the component or s'onorous sounds, and com features ofnovelty hereln-- after more; particularly described and causin on.clearness or dis- 1 active constants- Thcse composite sound wavesvtranslated into elecexisting waves, such waves of the resultant complexcurrent waves causes loss of 'clcarness 1n the reproduced soundwavesywlnle anything that Patented May 24, 1910 4 causes a loss ofcurrent, as by dissipation,

eauses a loss of volume'or loudness. ,Thesedisturbing influences have,been largely overcome-as regards their effect in the transmit ting andreceiving devices,.but the numerous 4 attempts to overcome them intheex'ternal circuithave' been, onlypartially'successful.. Thedisturbing influences which we here have more. particularly in mind arethe self-inductive and SO 31 218 we are aware,

the electrostatic capacity of the line or ex-'.- I

ternal circuit; Both of these influences re- .duce the amplitude of thecurrent waves an consequently cause a loss of volume; an

both also cause a loss of clearness or sharpuses; the effect ofelectrostatic capacity, or static induction, being to round off thecrate of the waves, and the effect of both self and static inductionbeing to retardation of base for vibrations (the component waves? ofdifierent periods, thus interference and a resultant deforme *waves Itwill therefore be seen that 'ifgood transmitting and receivingap eratusbe employed, the successful telep 9111C.

roduce an unequal I transmission of speechdepends on the Selfinductiveand the electrostatic capacity or condenser effect of the externalcircuit, and

hence it is desirable to reduce these characteristics of the line' tothe minimum.

In the transmission of a simple electrical h characterized by high len'resistance electrostatic capacity and inductive leakages, the I energylost or dissipated is proportional to and expressible in simple termsofthere of the systems, and there is no distortion of the wave form. Such,however, is not the caseforja comp trical wave composed of a pluralityof coin the telephonic transmission of the human voice or other sonoroussounds composed of aprime on fundamental In the latter case, eachconstituent wave of the-series is differently and independentlyaffected, and hence the resultant wave form at the distant end orterminus of transmislex elecas the waves involved and an ascendingseries of partials correspondipg'to overtones ,or characteristics ofarticulat on and quality. I

sion is nolonger identical with the initial wave form impressed upon theconductbr.

This is due to the physical fact that each wave is oppositely as well asdifferently affected by the electro-magnetie'and electro'w staticconstantsjof the system, though both conspire" to discriminate in favorof thelower' while retarding or attenuating the upper harmonics directlyas the frequency,

resulting in the loss of articulation and the natural characteristics ofspeech which are dependent .A pon .the transmission' of'. the upperharmonics or overtones, and while conceding that the greatest losses areprop 'erly chargeable to the dissipation'of the main line conductors,owi'n researches of" the subject -experimentally with commercial andartifieial circuit's'-have confirmed us in the opinionthat, so far aslong aerial or cable lines are'concern'ed, operating under actual]conditions, which might' be called existing j meteorological conditions,little if anything of average or' permanent value is to be obtained bytuning or readjustment of the line constants, and,

so far as we are aware, there exists at the,

present time no. commercially successful method orsystemof transmission,telephone relay, or repeater,

Various attempts from time to time have been made to deviseelectromechanical apparatus capable of replenishingthe current 'at someintermediate point of the circuit,

or adapted to transfer the messages of one telephone circuit to another,and thereby either to increase the length of line that can beoperatedsatisfactorily, or under other 'conditions to enable thereceiver to 'rcpro duce the transmitted message with increased loudness.These 'eiforts,howevcr, have uniformly been unsuccessful andunproductive of practical result, and it is a fact -that nothing of thekind isjn practical oncommercial use at the present time iniconnectionwith telephonecircuits anywhere, for though in some instances the soundsrepro duced by the receiver actuated by the replensociatecl conductorsis a great hindrance toeconom c'fransrmssmn and a preventive oftransmission through undergroundcables of anygreat length. The limit ofdistance to which speech can he telephonically transmitted, so as to becommercially intelligible is:

to their elec-- trical'characteristics, as outlined above, our.

not caused by jan'y' losses due to capacity. itself, which .is afunction of the medium surroundingthe conductor or pair ofconduct0rs,-by which it is ca able of stormg up and certain amount ofloss, known 'as dielectric ever, is trifling when compared tozthe other.Inore thoroug 1 y understood by considering that there are twocomponentsof current presentinj the conductor, one in phase with .theelectro-motive force, and tending to do us'efulwork at the receivingend, and the advance oftheelectro-motive force, representin" asuccessive chargin and discharging 0 t e medium surroun mg the'conduc--tor. This latter current may be, and is, in a tele hone cable,many'times greater than the use ul current. The '-resultant current atthe transmitting end is therefore larger than the usefulcurrenttransmitted tothe receivingegd. This roduces C R lossesthroughgreater than would occur if the current at thextransmitting-endwere the same as that at the receiving end. It 'isobvious, therefore,that anything which will diminish the attenuation of the current flowingthrough medium, will increase the efficiency of the circuit. v It hasbeen proposed for a number of years, .to obviate the excessive chargingcurrent existing in a circuit ofthis kind, by introducin -into thecircuit, in various manners, reactance coils which should cause thecurrent of equal and opposite effect to the capacity .current in thecable or circuit, and annul it. -None of these proved eflectual whentried in actual service until recently, when the theory of the designand placing of such loading coils was evolved, and it was found that ifductors .at roper "intervals, which are determinable y mathematics, theefficiency many disadvantages'of this arrangement, however, prominentamong which is the expense' ofithe coils themselves, and in undergroundtelephone cable work, the expense of the frequent building of vaults andboxes to contain these coils. To this we may add the 'difiiculty ofaccess to these coils which are embedded. in an insulatingv compound,and cannot be repaired without removing the entire containingliox, andthe difiiculty due to magnetic induction between different circuits dueto the'overlapping magnetic fields of these reactive coils, and againcircuits loaded with these coils are very diliicult to for 22 gagecabl'e'ii i l iihiles; 1 9' vgage-cable 25 miles; 16. gage cable 44miles. This 1s restoring energy to t e circuit. There is ahysteresis-due to this process, which, howlosses of "ener .finthe'cable." This maybe other a capacity current, a quarter'period in outtlfiifsentire. ength of the conductor, far .i

the conductor, by lowering the .;amount of current necessary to chargethe surrounding they were arranged in series with the con- I oftransmission was increased. There are operate over, that is to say, whenloaded ciredits are connected together, transmission of speech ispoorer, due to the fact that the cir; cuits have different timeconstants and so cause a'reflex action to -the-voice currents.

The object of our invention is to avoid the objectionable. features ofthe aforesaid ar- .rangements, .and to secure the effective reactanceinlong conductors and cables, necessarytoneutralize the capacity thereof,in a simple, inexpensive, and practical manner.

The nature of our invention will be more readily comprehended inconnection with the preferred type of apparatus, and thereforereferencewill now be made to they an:

.nexed' drawing wherein: such apparatus is illustrated diagrammatically.

1 g 1 ShOWS a system involvingthe application of our invention totelephonic transmission; Fig.2 is a diagrammatic view of a telephonesystem involving the application.of .our invention, and showing thetransmitting and receiving appliances ateach end of the line; Fig. 3is'adiagram showing graphically thecurrent waves whenin phase; Fig. 4 is adiagram showing current waves as displaced in phase by our invention;Fig. 5 1s a diagram which shows graphically the. condition, of thecurrent waves in the external circuit arising from the application ofour invention; Fig. 6 shows diagrammatically a. system of two stations,each adapted to transmit or receive at will, the necessary changes inconnections being made by a manually operated switch; -Fig. 7 showsdiagrammatically a single station adapted to-transmit or receive atwill, and equip ed with an automatic switch for effecting t cnecessarychanges-in the conprimary windings, connected in multiple witheach other and-in series with a telephone transmitter 5 'and a battery6.-- I, and 8,arethe two wires of the external ciredit, and in seriestherewith is the second- .ary winding 9 of the transformer at the othercnd'of the circuit. 10 indicates the primary of the transformer, inseries with the transmitter-l1 and battery- 12. The receivers at the twoends of thecircuit are in series with the transformer secondaries andare designated by 13 and 14. 15 is an impedancecoil of proper value, aswill be fully explained presently, inserted in either line,

.and preferably close to the secondary 1 or 2', as the 'case'maybe.

16 isa.surging or buffer line, open or: grounded by preference open, andpreferably Of '& ength greater than one wave length. This isurging'lin'eisconnected at the neutral point between.tho'

secondaries land V The operationof'this of our knowiledge and bel1ef,'asfollows: The

w s the best currents produced the primaries 3 and 4by the sound wavesentering the transmitter 5 are reproduce in the second try windings 1vand 2.. These induced currents are of course in phase, and would, in asimple sing e phase circuit; add up but the line 16 permits a surgetotake place in it, thus operating like a buffer,- i

as-it were, so that the independence of the- .two secondary currents ispreserved. The

current from secondary 1 is, by the impedance 15, caused to laapproximately 90 behind the E. 'M. F., w ile the current in the otherline, flowing fromthe secondary 2, is by the electrostatic ca acityor'condenser-efi'ect existing between inc 8 and the surging line 16caused to lead the E. M. F. by approximately in the line8, until theimpedance at the i'eceiving station is reached. .-.The result is an outof phase condition tothe extent of approximately 180 difference betweentwo currentsin lines'i7 and 8. -This condition is indicatedgraphically-in Figs. 4-

and 5, Fig. 3 illustrates thephase' relation of the currents in anordinary s'stem' and it will be noted that the polarity o the currentwave in one line is always of contrary sign to the current wave in theother, and consequently theca acity efi'ec't between the two is maximum.n the other hand, it will-be seen that in Figs. t and 5 conditions ofour method, the polarities in- '100 -wh1ch represent 'what would bethe-ideal thetwo lines are always of the same sign;

and, consequently, if such ideal conditions could be attained inpractice, the self-induction and capacity efiect between the lines 7vould be zero. When the currents reach the secondary 9 of thetransformer at the other end of the line, the impedance'of the secondarycausesthe phase relation to be restored,

at least partially, to the original relation, so

that there is produced a difierence of potential across the receivingtransformer, and the current waves are consequently translated intosound' waves.

more nearly the currents in the two lines are kept 180 out of phase,-andthe more nearly "1 15 .It will be understood, of-course, that thetheyare brought into phase at the receiving transformer, the better thespeech transmission'; and it is therefore desirable to aproxirnate theseconditions as far as possible.

- t is obvious for various reasons, chiefly the factthat the componentsof the waves are of different-.periodicities and arethereforedifferently afit'ected by the impedance and by the electrostaticcapacity or condenser effect between the surging line and the circuit,the current waves, which reach the receiver at the otherend of the lineare never identical the impedanceand the condensereffectju st mentioned-that "a considerable -.phase d s placement may-bezproducedwithout'defornb;

&.

with" those produced in' the transmitter; but it'is possib e to soPIOPOl'tlOD the values of mg the current wavesto an impracticableextent. The periodicity of the'ielephone, current is usuallyassumed. to"be 750 ;-and: on

' this assumption, with a transmitter trans- 'former of ;6ohmsresistance in its primary .and 175 ohms inits secondary, and aprcurrent of .14 volts, extensive expenments and practical'tests haveindicated -an impedance of 1100-0hms as the best value, :whatever he.the length I. of the 'e x;ternal orv transmission circuit; In general,:we prefer,

as already stated, .to .make the surging ling,

16, slightly longerthan a wave length, as

suming'the riodicity of the current to 'be 750,. but di erent conditionsmay make a different :Ien-gth iadvisable, either longer or shorter asvthe-caseimay 'be,'-or it may .even.

be extended and connected 'withthe distantstation. Fig. 1 isdesigne'djto re resent .m the simplest :way the operation 0 ourinvention,

and no provision is madeinthis figure for transmitting from thetransmitter 11.- It

" ;-wi-11':be understood,:of'course that thisend of the'line must forthat-purpose beequippedx like the other .end, as clearly shown in Fig.-2.

' Under some circumstances itis found desirablethat when e'ithers'et ofinstruments is receiving, the impedance, as 15) at'thatendof'theilineshould he cutout. It-may be advisable-at times tocutout half'ofzthe' trans- :formersecondary whe'nireceivingpA com- 1 Q pletesystem; for" transmitting and receiving from each end of the line isshownby'means of the simple diagram," Fig. 6.. It will be seen that eachstatiomis equipped-alike. At each there is a. double pole switch 17, inthe neu- -tral line, and in the main line, by which the impedance, theneutral line, and half of the secondary w nding may be out out at will.'-When it.is desiredfto receive, this switch-is opened, as'atthe rightotzF-ig'. 6;

and when transmitting, {the switch is closed,

' as at the #left. When the 'user is through .50 person at the other enddesires to talk, he;

talking, he opens his switch 17, and if-the the other-branch.

.- As long as thestation is receivlng lthe relay remainsneutral.hutwhenevei' the user speaks into the transmitter, .the...pulsatingcurrent ythereby setup unhalanc'esthe branches, so that the.magnetnowdraws'over armature 25,.and th e con a springs am .27; a

wire 30, spring 26,- wire'3l secondary 32,

In the .position for receiving, as, shown-in Fig. "Z, the circuit isasffollows: ffrom the distant stationyto terminal 28, springa27,

wire 33, receiver 33*,and terminal .34, .back to thelother station.--When the-switch is thrown, as above explained, the primary transmittingcircuit is throu h transmitter 35, battery 36, wire- 37, .re lay coilsand h branches, primary windings 3850f the transmitt-ing transformer,and wire 39 back -.to

the transmitter. .The secondary circuit is .then as-follo-ws:secondaries32 and 40, wire' I .41, impedance 42, wire 43, contact spring27, xvii-e45, terminal 28 th'ro h the distant station to terminal 34,then-wire 33 back to thesecondary winding 32. As-soon as the user-ceasesspeaking into the transmitter 35, .the balance of the relay branches isrestored,

' position shown in the figure.- It will be oh- 0 and the springs 26, 27are; restored tothe servedthat when the switch .is in the transmittingposition the wire 31, from. the neutral point between the secondary wind.ings, -is-.connected with the neutral or surging line extending fromterminal .46, by

spring 26, and wire 47. When the switch I is thrown over,-;this path toterminal46 is 1brokenby spring 26 leaving the contact or wire 47.

Fig.8 is a diagram showing ;a station equipped with theswitch justdescribed, and

also with a convenient arrangement of signaling devices, utilizi ourinvention in the .latter as well as irtt e telephone system. In'thisfigure, 48, designates ,a hand-open ated. magneto machine ofordinarytype, in-

which turning .the crank to call the other station causes the crankshaft to actuatea 'switch at'the other end of the same, indicated by48.This method of operating the magneto switch is common and wellfinderstood. The hook on which the receiver hangs when :not in. use isindicated at 50.

The weight of the receiver depresses the "switch arm 51, thus changingthe connection ,thereat 1n the usual manner.

station is connected by line wires to the terminals 28 and 34, and fromterminal'46 extends the neutral or'surging line.

The distant- When the'systemis not in use, the receiver hangs on thehook 50, and the rela switch is in the normal,'or receiving position, asin Fig. 7.. If new the otherstation signals, the circuit is establishedas follows: terminal 28, wire 28, impedance 28",,bel1 coils 52, wire53,'springs .54 and 55 at the hook switch, wire.56, springs.- 57 and 58at the magneto switch, 56", to terminal 136 lishing the 1 followingreceiving circuits:

34, back to the signaling station. The person; ca-lled then removes hisreceiver, estab- --;trom the-other station to terminal 28, wire4.4,.spring 2:7, wire130, spring 26, wire 31, secondary winding 32, wire33, receiver 33*,

wire 58,,spring's 59 and 55 at the hook' "switch, wire 56, springs 57and 58 at the the transmitter.

magneto switch, wire 56, and terminal 34 back to the other' 'station.

When the user at the station at this end of the linejdesires to reply,he speaks into. the transmltter, whereupon the relay is unbalanced andthe armature drawn over, as

previously e xplained,.to the position shown in Fig. 8.

The primary, transmitting circuit is thus established throughtransm1tter3 5, battery 36, wire 60, springs 61 and 62 at the hookswitch, wire 37, relay coils 22 and branches, primary windings 38, andwire 39'back -to The secondary transmitting circuit is -then as follows:secondary 'windin 32 and 40, wire 63, spring 64 at the hoo switch, arm'51, wire 65, impedance m, wire .43, spring 27 at the relay, wire 44,.

terminal 28 to the other station, then back through terminal 34, wire56, spring 58 and 57 at the magneto switch, wire 56, spring erator or ma55, spring 59,wire 58, receiver 33, and wire 33 back to the secondarywinding 32.

, When-the system is in its normal condition, that is, with the receiveron the hook,

and with the relay switch in the position shown in Fig. 7, the otherstation is signaled in the following'manner: The hand geneto machine 48is operated,

which not 0 y supplies the signaling cur.-

.rent, but also 0 crates the switch 49, as

28, wire 28, .50

already explaine resulting in the following circuit being established:from the armature through wire 66, rimary windings -67 of the signalingtrans orzneror repeat- 'ing coil, wire 68, springs 69 and 70, at themagneto switch, and back to the armature. The secondary signalingcircuit is then as follows: secondary windings 71 and 72, wire 73,springs 74 and 75,'wire 76, impedance through terminal 28 to the distantstation, then back to terminal. 34, wire 56, springs 58 and 77 at the maeto' switch,-wire 78 back to the secondary 1.

VVlienthe relay switch is in theposition shown (Fig. 8,) that is, in thetransmitting.

position, the neutral point between the sec ondary windings 32 and 40 isconnected. by wire 31, spring 26 and wires 47 and 79 to the terminal 46,from which extends the neutral or surging line. When the system is notin use, that is, with the receiver on the hook 50, the surging linewhich extends from terminal" 46 is connected between the bell magnets bywires 7!), 80,31, springs 82 and- 83 at the magneto switch, wire 84,springs 85 and 86 at the hook switch, and wire 87.

Removing the receiver from the hook-breaks this connection by separatingsprings 85 and 86, so that the surging line extending from terminal 46will not be effective through wire 28, one of the bell magnets-52, wire87 etc.- The line losses in telephone transmission circuits, due-to selfand static induction, are

of vital'importance; and, inasmuch as our mvention overcomes theseeffects to so considerable a degree, we are enabled to'deliver tothetranslating device, whatever it may be, a larger roportionofthegenerated current than as,-so far as we are aware,

been possible in the systems heretofore pro posed.

' While we have shown ually operated switches in connection with our' imrovement, it will'be readily underautomatic and manstoodt at, in so faras the tIfiIlSIIllSSlOIl and,

receiving of electrical energy is; concerned, the action, ascontemplated by our invention, may be carried out with equal success'bythe simple-arrangement of lines and connections,

: as shown in Figs. 1 and 2 wherein such ap- 90 pliances are not employeInconclusion, it should be stated that while the line conductors may bein any inductive position relativeto each other, they must, in everycase, be arranged in inductive relation to fthe surging line, becausethe action between this line and the transmission lines is, as alreadyexplained, essential to the invention.

ing line-extends to the receiving or translat- It is of course evidentthat where the surgin" devices, the line conductors, if in-inducta iverelat1on thereto, are also 1n inductive relation to each other. Wecla1m:-

1. In a telephone system, the combination mitting and receivingapparatus,'of means at each station for a'l'teringnthephase rela- 'tionof the'currents, and means at each station for cuttingsaidphase-altering means in or out of the circuit at will.

3, In a telephone system, the combination with a circuit and a pluralityof stations thereon, each provided with transmitting 'affd'receivingapparatus, a differential relay at each station, dependent for operationupon, actuation, of the transmitting apparatus by sound waves enteringthe same, for changing the station from receiving to transmittingcondition,

3 t. In a telephone system, the combinationw th a metal iccircuit, anda-plurality of stations thereon, each provided with trans- 'mitting andre'ceivin apparatusyof means ateach station for a terlng thephase rela--tion of the currents in the twhsides of the 7 said phase altering meansin circuit.

v 5.' In 'a telephone system, the combinationof a metallic circuitthe-sides of which are in inductive relation' to each other, a plurality of stations thereon, transmitting and receiving apparatus at eachstation, and

means in series with the circuit cooperating with means=in inductiverelation with both sides of-the circuit for producing in. bothsides ofthe circuitat the same time currents of like polarity, and for restoringsaidfourrents to their original polarity;

6. In a telephone system, the combination with a circuit, a plurality ofstations thereon iea ch provided with'a transmitting and re-. 'ceivingappliance, and means for producing in the opposite sides of saidcircuit-between connected stations of the circuit at the same timecurrents of like polarity. a

v 7. In a telephone system, the combination with a circuit, a pluralityof stations thereon each provided with a transmitting and'receivingappliance, of means for producing in the opposite sides ofsaid circuitbetween connected stations at the same time currents of like polarity,and -means for restoring said currents to their original polarity at thereccivin station.

- 'tion with stations, each provided with trans i C intothe circuit atwill, of means arranged 8. In 'a te ephone system, the combination withstations, each provided with transmit-- ting and receivmgappliances, acircuit connecting said stations, of means interposed between thestations for altering'the phase relation of the currents during theirtrans- 45' mission over the lines of the circuit.

9. In a system of telephony, the combinawhich'are in inductive relationto each other,

of means in series with the circuit coiiperat:

mg with means in inductive relation with both sides of sald clrcuit forproduc ng 1n said' currents to their on nal polarity. i

10. In a system of telep ony, the combination of a metallic telephonecirc'uit,*the sides of whiclrarein.inductive relation to each pliances,

other, a plurality of stations thereon each.

provided with transmitting and receiving apfor retardingthe current inone hranclrof said circuit and correspondingly advancing the current inthe other side of said circuit,

of means in series with said circuit' and means in inductive relation"to the cir- -cu1t -fo'r correspondingly advancing the rev tardedcurrent and retarding the advanced current.-- v o 11. In a telehone-system, the comhina-I {0 tion with anal metallic circuit the side'sof which are ,in'indu'ctive relationto each'other, and a plurality ofstations thereon each provide'dwith transmitting and receiving aplieirices, of an impedance coil .in each .si e 5' of said circuit, anda surging line in inductiverelation to both sides of said circuit.

12. In a telephone system, the combination with an all metallic'circuit,the sides of 13.= In a telephone system, the combina- ,tionwith a metalliccircuit and a station thereon provided with bothtelephone trans} 'mitting and receiving appliances, of means, arrangedadjacent to the-saidstation, comprising an impedance in the circuit, anda sui'gin line in inductive-relation to both the lines, tc said meanscooperating to change {he phase relations of the currents on the me. v a

14. In a telephone system, the combination with a metallic circuitandstations thereon each .provided with both telephone transmitting andreceiving appliances, of

tion for. altering the normal phase relations of thecurrents passingover the line of the circuit, and other means located adjacent to areceiving station for restoring the norbeing delivered to the receivingappliances.

:15. In a telephone systenn-the combination with a circuit, a plurality'of stations thereon, telephone transmitting and receivstation,- andmeans for bringing the said- --teleph0ne apparatus or .signaling devicesadjacent to one station for altering'the normal phase relations thecircuit, and means near another station for restoring the normal phaserelations of the currents before theyare delivered to the receivingappliances. v 16. In a telephone system, tion with a circuit, aplurality of stations thereon, telephone transmitting and receivingapparatus, and signaling. devices at each station, the signaling devicesbeing normadly in the circuit when the system is at 125 rest, and thetelephone apparatus being arranged to be brought into the-circuit when"the system is in use, whereby any stat on -may become a sending stationand anctner a receiving Statiom-of means arrangcd'adjaiso meansarranged'adjacent to a sending star ma-l phase relations of the currentsbefore ing apparatus and signaling devices at each of the currents sentover the combina- 1 20 cent to. a sending station for altering the ingthe normal phase relations of the cur- 15 normal phase relations of thecurrents sent rents sent over the circuit, and other means over'thecircuit, and means near a receiving also in permanent cooperativerelation with station for restoring the phase relations hf, the circuitarranged near another station for the currents. restoring the normalphase relations of the 17. In a telephone system, the eombinacurrents.20

*tion with a circuit, a plurality of stations In testimony whereof, wehave signed our thereon, telephone transmitting and receivnames to thisspecification, in presence of ing apparatus and signaling devices ateach two subscribing witnesses. station, and means for bringing the saidWILLIAM F. GRADOLPH.

telephone apparatus or the signaling (1e- VILLIAM C. HAHNE. vices intothe circuit at'will, of means in Witnesses:

ermanent cooperative relation with the cir- A. R. KELso,

wit arranged adjacent to a station for alter- HOUSTON BOND.

